THURSDAY, April 12 (HealthDay News) -- Health investigators have confirmed that a bat that flew through the cabin of a U.S. commercial airliner last summer did not transmit rabies to 45 of 50 passengers assessed, the three flight crew members or 16 ground crew members who were in close proximity to the winged stowaway.

The U.S. Centers for Disease Control and Prevention located and interviewed nearly all of the passengers on board the early morning flight that departed from Madison, Wis., last August. Neither the passengers nor any crew members were in physical contact with the bat or its saliva, and all said they were alert during the flight, the CDC said.

The bat, which took flight in the aircraft cabin shortly after takeoff, was temporarily barricaded in a restroom, the report said. But after the plane returned to the airport, the feared intruder escaped outdoors and could not be tested for rabies.

A series of injections can prevent rabies in people exposed to the virus, but the shots must be given right away, or the disease can be fatal. While none of those on board required vaccination in this instance, bats active in daylight can pose risks for rabies transmission, the CDC warned in its Morbidity and Mortality Weekly Report, published Thursday.

"Although a bat, or any wildlife, aboard a commercial airliner is unlikely, public health practitioners should be prepared to respond to potential exposures to rabies and other infectious agents, including during air travel," the CDC said in a statement.

In the previous decade, 21 humans in the United States suffered rabies infections, and bats were the cause in 15 cases, the CDC said.

An inspection of the airport facilities revealed no other evidence of bat activity or droppings, but the CDC made several recommendations to reduce the possibility of bat exposure. It suggested the airport place netting over chinks and crevices that might house bats, and said the jetways at each gate should be extended and retracted before the first morning flight. Airport employees should also be trained on correct procedures for bat capture and preparation for testing, the report said.